When cast crown restorative treatment, prosthodontic treatment for missing teeth, or the like is required for restoring teeth and the like, an imprint of abutment teeth and the like is taken first. Next, a model made of gypsum or the like is produced through use of the taken imprint. Then, a prosthetic appliance is produced based on the model, and the produced prosthetic appliance is attached to the abutment teeth and the like. The imprint of the abutment teeth and the like is called an impression, and a curing material for taking the impression is called an impression material. As the impression material, for example, there are used an alginate impression material, an agar impression material, a silicone rubber impression material, a polysulfide rubber impression material, and a polyether rubber impression material. Of those, an alginate impression material is most widely used because it is inexpensive and easy in handling.
There are proposals concerning various types of the alginate impression material. For example, the applicant of the present application has already proposed an alginate impression material containing an organic hydroxy compound in which a value obtained by dividing a molecular weight by the number of hydroxyl groups in a molecule is less than 40 and the number of hydroxy groups in one molecule is 3 or more, for the purpose of, for example, improving impression material properties (Patent Literatures 1 and 2). There is also a proposal concerning an alginate impression material blended with a sugar alcohol such as xylite, a sucrose fatty acid ester, or the like, in order to prevent evaporation of moisture from a cured product (Patent Literatures 3 and 4).
Work for taking an impression through use of the alginate impression material is carried out according to the following procedures. First, a product obtained by kneading constituents of the alginate impression material is mounted on an impression tray made into a similar shape to that of arrangement of teeth. Next, the tray on which the impression material is mounted is pressed against the teeth so that the tray covers the teeth in the oral cavity. Then, after the alginate impression material has been cured, an integrated product of the alginate impression material and the tray is removed from the teeth and taken out of the oral cavity.
In using the alginate impression material, main components including an alginic acid salt, a gelling reaction agent such as calcium sulfate, water, and the like are kneaded together to be used. In addition, as the alginate impression material in a state before use, in order to ensure its storage stability, there are known a powder type alginate impression material in which solid contents obtained by removing water are formed into powder and a paste type alginate impression material in which a paste containing an alginic acid salt and water as main components (base material paste) is used in combination with a paste containing a gelling reaction agent as a main component (curing agent paste). In addition, upon use, the powder and water are kneaded together in the powder type alginate impression material, and the two kinds of pastes are kneaded together in the paste type alginate impression material.
The powder type alginate impression material requires proficient skills based on handwork upon kneading work. On the other hand, in the paste type alginate impression material, automation and labor saving of kneading work can be easily achieved through use of a dedicated kneading apparatus for kneading the base material paste and the curing agent paste together. Therefore, in recent years, the paste type alginate impression material has become popular as an alternative to the powder type alginate impression material.